For the purposes of this document, IMON is the name of a signal that represents the level of output current for a voltage output of a voltage regulator. Other documents may use other names to describe the same thing. Typically, there is a separate IMON for each VR output voltage (5 V, 12 V, etc.). Since power is equal to voltage times current, the accuracy of the processor power calculation is directly proportional to the accuracy of the IMON signal. This accuracy may be important. For example, if the processor concludes it is not consuming its power allocation, it may go into Turbo mode and if it determines it is exceeding its power allocation, it may throttle its performance. Therefore, inaccuracies in the IMON signal may cause the processor to either underperform or to exceed its designated performance goals.
VRs from the same manufacturing lot may have different accuracies. Therefore, an OEM may want VRs with an accuracy of +/−5%, but receive VRs with an accuracy of (for example) only +/−20%, the difference reflecting cost savings in the VR. This variance may cause a loss of performance in the associated processor. For example, a more expensive high performance processor may only achieve the performance of a cheaper low performance processor, simply because it mistakenly limits the power it receives from the VR based on an inaccurate IMON reading.